The present invention relates to a redundant induction (fuel) system for an internal combustion system and, in particular, a redundant induction system which converts a dry manifold to a mixed fuel manifold.
In a number of situations it would be useful to provide redundancy in various engine components, such as a situation where malfunction or interruption of engine power can create a safety hazard. Examples include engines for aircraft, engines for racing cars or other high-speed vehicles, engines for emergency use, such as emergency vehicle engines, emergency power sources and the like. Redundancy can also be useful for other less critical applications such as to avoid inconvenience that might result from engine failure or power interruption in ordinary automobile, powerboat, motorcycle engines, portable or fixed electrical generators and the like.
One system in which redundancy may be useful is an ignition system. A redundant ignition system is described in U.S. Pat. 5,713,338 filed Sep. 19, 1995 and incorporated herein by reference. Another system in which redundancy may be useful is an induction (fuel) system. In some types of internal combustion engines, the fuel system is a sequential multi-port fuel injection system, permitting ignition timing and mixture to be adjusted individually for each cylinder and each engine revolution. Some such engines provide a so-called xe2x80x9climp homexe2x80x9d made upon (at least partial) failure of the fuel system. However, many such limp home modes provide for severely reduced power output such as a power output of only about 20 to 40 percent normal power. While such limp home mode may be suitable for some applications (such as automobile applications), such severely-reduced power output would be inappropriate for aircraft or other applications. In many aircraft, it is infeasible to attempt a powered landing with only 20 to 40 percent normal power available. Accordingly, it would be useful to provide an induction (fuel) system in which, after (at least partial) failure, a redundant induction (fuel) mode is available producing sufficient power for powered landings such as around 60 to 80 percent normal power (or more).
Many previous multiport injection engines use numerous components to achieve desired functionality including individual sensors for cylinders, individually adjustable fuel injectors for each cylinder, one or more computer, or other, control devices and the like. While it might be possible to provide an engine with a fully redundant multiport system, since failure of the induction system can result from failure of any of the multitude of components, adequate safety for a fully redundant multiport sequential injection system, would require redundancy in each component, so that a fully redundant multi-port sequential system would involve providing two (or more) of each of the sensors, injectors, computers and similar components. Such a system would be extremely costly and complicated to design, fabricate and maintain. Moreover, the additional weight involved in providing all components in redundant fashion may be unacceptable for aircraft or similar applications. Accordingly, it would be useful to provide an induction (fuel) system for an internal combustion engine which can be implemented without duplicating all of the various components of the typical multiport sequential injection system.
Many previous sequential multiport injection systems employ a pressurized xe2x80x9cbusxe2x80x9d used to provide fuel to the fuel injectors. Typically, there is much more fuel in the bus at any one time than is used during an engine cycle. In many systems, in order to maintain the desired fuel flow and pressure in the bus, the majority of fuel provided to the bus is circulated, i.e. most of the fuel provided to the bus is returned to the fuel tank for later recirculation onto the bus. While this situation is reasonable to implement, when the engine is used in, e.g., an automobile, typically having a single fuel tank, many aircraft have two or more fuel tanks. Often, the (typically manual) controls for routing fuel from various tanks to the engine involve multiple decisions and valve or control manipulations to achieve the desired result. When it is desired to provide a multiport sequential injection engine in an aircraft, having a bus as described above, the decisions and manipulations and the design of conduits and valves involved in properly controlling the flow of fuel are made relatively more complex, e.g. because the need to provide for return of fuel from the bus to the proper fuel tank. The complexity of such manipulations presents a safety issue since erroneous manipulations or decisions can be lead to fuel starvation with potentially catastrophic results. The complexity of the conduit and other designs leads to a system that is costly to fabricate and maintain. Accordingly, it would be useful to provide a multiport sequential injection system which avoids the recirculation of fuel from a bus to one or more of a plurality of fuel tanks.
Additionally, in the above-described bus system, since the majority of fuel entering the bus is merely returned to a fuel tank, it becomes difficult to accurately measure the rate of fuel consumption since metering the flow through the fuel bus is not an indication of consumption. Although it may be possible to measure or calculate the difference between flow out of the fuel tank and return flow into the fuel tank, such systems are relatively expensive to implement and maintain. Accordingly, it would be useful to provide a multiport and sequential injection system employing a bus, which provides a relatively simple and inexpensive fashion of measuring fuel consumption.
The present invention, in one aspect, involves providing a solenoid-controlled fuel source, such as a fuel injector, in the plenum of the (normally dry) engine air manifold. Upon failure of the primary (multiport sequential) injection system, the solenoid causes fuel to be injected into the (normally dry) air manifold thus providing a source of fuel/air mixture to the cylinders for continued operation (albeit at somewhat reduced power). In one embodiment, a degree of power control is available by providing a barrel or other valve, adjustable by the operator, between the solenoid and the injector. In situations where two or more fuel tanks are involved in the fuel system, an embodiment of the present invention involves providing a header tank which acts as both the source for the multiport sequential injection bus and a sink for fuel recirculated from the bus, obviating the need for decisions or manipulations regarding the destination for recirculated fuel. In this fashion, a flow meter coupled to the header tank (preferably measuring flow into the tank) provides an accurate indication of fuel usage (such as engine consumption plus any venting of the header tank).
In one embodiment, the plenum of an engine air manifold, coupled to engine cylinders, is provided with a fuel injector. A solenoid prevents supply of fuel to the plenum fuel injector during normal operation of the engine. Upon failure of the primary fuel system, solenoid opens to provide a fuel/air mixture via the manifold, to the engine cylinders, converting the manifold from a dry manifold to a fuel/air mixture manifold. The fuel bus of the primary fuel system preferably receives fuel from, and returns fuel to, a header tank, rather than directly from and to one or more fuel tanks.